Kyle Stephenson, 29, now of no fixed address, was sentenced at York Crown Court on Friday after what a detective described as one of the "most harrowing and disturbing" cases he had been involved with.
Stephenson - described as "vile and manipulative" by police - had been due to stand trial this week but decided to plead guilty to the offences against the boy and the girl.
Stephenson also admitted committing bestiality after police recovered conclusive video evidence.
The Judge took this offence into consideration when passing sentence, which also subjected him to a life-time Sexual Harm Prevention Order and placed him on the Sex Offenders’ Register indefinitely. He also has to serve an extra year on licence.
Stephenson was arrested on 31 January 2021 following a complaint made by the boy and he has remained in custody since being charged.
The offences were committed between then and January 2020.
The dog Stephenson abused has died from an illness.
Detective Constable Steve Monty, of Scarborough CID, who led the investigation, said Stephenson is now facing the consequences of his depraved actions
He said: “This is one of the most harrowing and disturbing cases I have been involved in. My heart goes out to the brave young victims who have endured immense trauma caused by this vile and manipulative man.
“Their true courage, together with support from loved ones, will hopefully give them the strength to rebuild their lives and move forward from this dreadful experience.”
Det Con Monty added: “As for Stephenson, he has rightfully been brought to justice and is now facing the full consequences of his depraved and disgusting actions.
“My message to victims of child abuse, no matter when it occurred, is that the police will support you in a highly professional and sensitive way throughout an investigation and court case.
“Please don’t hesitate to seek our help or obtain support from specialist services that are readily available to victims.”